Epidemiologists have postulated that one of the major risk factors in breast cancer is the association of dietary factors. The role of diet and dietary components in breast cancer prevention has been widely discussed during the past decade. Recent studies suggest that the risk of breast cancer has been inversely associated with vegetable and fruit consumption. There is increasing evidence that a number of biological agents in the diet may exert a significant influence on the growth and differentiation of normal and malignant breast epithelium. Beta-carotene is most abundant in vegetable and fruits, serum levels of Beta-carotene are responsive to dietary intake, and exert the activity of antioxidant and anticarcinogenesis. The studies in this proposal are aimed at identifying molecular targets of carotenoids in mammary cells that may serve as potential intermediate endpoints for dietary intervention and chemoprevention studies. The objective of this study is to identify, characterize and clinically apply a set of genes that are responsive directly or indirectly by carotenoids and/or retinoic acid in human breast cancer. Such new data will have a great impact on our knowledge of development, differentiation, cell growth, and cancer therapeutics. The hypothesis to be tested is that the effects of carotenoids on the process of anti-carcinogenesis or cancer prevention through cellular differentiation and growth inhibitions may result primarily or exclusively from the ability of these molecules to regulate the expression of specific genes. Specifically, we propose: i) to examine whether expression of various known tumor suppressor genes (RB, p53, and nm23) can be enhanced with the treatment of carotenoids or retinoic acid in normal mammary cells. We will also determine whether the levels of oncogene expression in tumor mammary cells can be modulated by the effect of these agents; 2) to determine whether previously identified genes that are down-regulated in breast tumor cells can be expressed by the action of carotenoids in breast tumor cell lines; 3) to isolate the carotenoids- responsive genes from normal mammary cells using subtractive hybridization technique. We will also determine the expression patterns of these genes in carotenoid or retinoid treated breast tumor cells; 4) access the effects of dietary carotenoids on the expression of genes isolated to in vivo specimens from different stages of breast cancer patients. A major effort will center on isolation and characterization of the carotenoids-responsive genes. This proposal may provide insight into the molecular mechanism of the action of carotenoids for use in breast cancer chemoprevention.